1. Field of Invention
The present invention relates to a receiver for a LAN system and, more particularly, to a receiver installed in a computer for receiving signals transmitted in a home phone-lines LAN system and distinguishing a valid signal and a collision backoff signal from noises in real time.
2. Related Art
Along with the prospering electronic IC industries and information technologies in recent years, network systems play an important role in daily life. In particular, because the phone-lines in home have already installed for general telephone network, it is convenience to use the same home phone-lines as the transmission medium in home local area network (hereinafter xe2x80x9cHLANxe2x80x9d) systems. Each computer in the HLAN system can install a receiver to receive the signals transmitted via the phone lines.
As shown in FIG. 1, a conventional receiver in a home phone-lines LAN system compliant with the HomePNA 2.0 specification comprises a QAM (quadrature amplitude modulation) demodulator 101 for providing the xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals from signal frames; an equalizer 102 for compensating the xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals for the distortion caused by transmission; a deconstellation 103 for converting the compensated xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals into data signal D; a detector 104 for distinguishing the xe2x80x9cvalid signal framexe2x80x9d and xe2x80x9ccollision backoff signal framexe2x80x9d from noises and other interference: and a data reading module 105 for reading in subsequent data signal when the signal frame is a valid signal frame.
However, in a conventional receiver described above, because the detector 104 is connected to the deconstellation 103, it can distinguish the valid signal frame and the collision backoff signal frame from noises only after the demodulation by the QAM 101, the distortion compensation by the equalizer 102, and the conversion to a data signal D by the deconstellation 103. Nevertheless, when the received signal RS contain too much interference, it will take longer time for the equalizer 102 to compensate for the distortion and thus the system might not be able to receive the valid signal in time.
In view of the foregoing, it is an object of the present invention to provide a receiver for a home phone-lines LAN system containing a signal match filter module which detects a received signal and determines whether received signal is a valid signal, collision backoff signal, or noise in real time.
In accordance with an aspect of the present invention, the receiver for a home phone-lines LAN system of the present invention comprises a QAM demodulator for demodulating the received signal into xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals; an equalizer connected to the QAM for compensating the xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals for the distortion; a deconstellation connected to the equalizer for converting the compensated xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals into data signal; a signal match filter module connected to the QAM demodulator for performing match operation to generate a match value; a detector connected to the signal match filter module for detecting the match value and outputting a frame type; and a data reading module connected to both the deconstellation and the detector for reading the transmission data when the frame type is a valid signal frame.
According to the receiver for a home phone-lines LAN system of the present invention, the signal match filter module comprises an adder connected to the QAM demodulator for adding up the xe2x80x9cIxe2x80x9d and xe2x80x9cQxe2x80x9d signals to generate a combined signal; and at least one set of cross-correlator for performing correlation operation on the combined signal and outputs a match value.
According to the receiver for a home phone-lines LAN system of the present invention, each cross-correlator comprises a plurality of shift buffers for shifting the combined signal; a plurality of multipliers having an input to receive the value stored in each shift buffer for multiplying the value and an identification value; and an adder for adding up the output values of the plurality of multipliers to generate the match value.
According to the receiver for a home phone-lines LAN system of the present invention, each cross-correlator comprises a RAM module for storing the data of combined signal circularly; a ROM module for storing the data of identification value; a multiplier for multiplying the data output from the RAM module and the data output from the ROM module; an accumulator for accumulating the value output from the multiplier; and a controller for controlling the action of the signal match filter module.